The present invention relates to the art of color proofing, and in particular, to an improved lamination assembly and roller for preparing prepress color proofs, such as by the use of pressure and heat to laminate media together.
Prepress color proofing is a procedure that is used by the printing industry for creating representative images of printed material to check for color balance and other important image quality control parameters, without the high cost and time that is required to actually produce printing plates and set up a printing press to produce an example of an intended image. These intended images may require several corrections and may be reproduced several times to satisfy or meet the requirements of the customers, resulting in a large loss of profits and ultimately higher costs to the customer.
Generally speaking, color proofs sometimes called xe2x80x9coff pressxe2x80x9d proofs or prepress proofs, are one of three types: namely (1) a color overlay that employs an image on a separate base for each color; (2) a single integral sheet process in which the separate color images are transferred by lamination onto a single base; and (3) a digital method in which the images are produced directly onto or transferred by lamination onto a single base from digital data.
In one typical process for a prepress color proofing system used in the printing industry, a multicolor original is separated into individual transparencies, called color separations, the three subtractive primaries and black. Typically a color scanner is used to create the color separations and in some instances more than four color separations are used. The color separations are then used to create a color proof sometimes called an xe2x80x9coff pressxe2x80x9d proof or prepress proof as described above.
A Kodak Color Proofing Laminator can be used to bond lamination sheets to receiver stock as a part of a color proofing system. The lamination sheets include a carrier and a layer of material to be applied to the receiver stock, which, in the case of the Kodak Color Proofing Laminator, is a color donor. A lamination sheet is laid upon the receiver stock with the color donor side sandwiched between the carrier and the receiver stock forming a lamination sandwich.
FIG. 1 shows a laminator 12 as described in U.S. Pat. No. 5,478,434. As shown in FIG. 1, a lamination sandwich 10 sits on an entrance table 20. A leading edge of lamination sandwich 10 is fed into a laminator 12 which includes an upper heated pressure roller and a lower heated pressure roller. Lamination sandwich 10 passes completely through the upper heated pressure roller and the lower heated pressure roller. Lamination sandwich 10 thereafter exits the upper heated pressure roller and the lower heated pressure roller and comes to rest on an exit table 14 undisturbed until the trailing edge is cool to the touch; whereupon the top-most carrier can be peeled away from receiver stock and from the transferred color donor. With the configuration of an upper heated pressure roller and a lower heated pressure roller as described above, the laminator is called a straight-through laminator. Further details of this type of lamination/de-lamination system can be found in the above patent. As an additional reference U.S. Pat. No. 5,203,942 describes a lamination/de-lamination system as applied to a drum laiminator.
While the above-described laminator works well for a some materials and in limited conditions, there are many conditions and materials that cannot be laminated successfully using the above-described laminator. One problem is the intended image shifting from one color to another such that the dots/image from one color to the next are not overlaid correctly causing a misregistration of the intended image. Also damage to the media may occur in the form of speckle, freckle, image wave or creases commonly know as rivers or valleys. Any of the above mentioned problems can render the intended image unacceptable to the customer.
The aforementioned problems are for the most part due to the heated pressure rollers and there application. The upper heated pressure roller and the lower heated pressure roller have hollow cores that are typically made of metal. The hollow portion of the core is for accepting a heating rod or lamp while a rubber layer or shell typically of silicone rubber is formed around the outside of core. Typically one of the heated pressure rollers will have a different durometer. Typically one heated pressure rollers of this type has a 50-60 SHORE A durometer and the other a 65-80 SHORE A durometer and in some cases they are the same SHORE A durometer. When the upper heated pressure roller and the lower heated pressure roller are pressed together they form a nip or indentation which is typically 7-10 mm wide and varies considerably along the length of the heated pressure rollers at a pressure of 40-80 PSI . Within the nip formed by the upper heated pressure roller and the lower heated pressure roller, lateral shear stresses and overdrive conditions are formed. These lateral sheer stresses and overdrive conditions act upon the media being laminated together to cause the intended image to shift from one color to another color. These lateral sheer stresses and overdrive conditions can also cause a defect in the final lamination in the form of creases commonly known as a rivers or valley, as described above. These lateral sheer stresses and overdrive conditions can also cause image growth which can be different with each color, causing the intended image to be misregistered from one color to the next color or to be larger than the original image or printed image. Also these lateral sheer stresses and overdrive conditions can cause the bond that holds the rubber on the core to fail letting the rubber to delaminate from the core.
An object of the present invention is to provide for an apparatus and method that overcome or reduces the drawbacks noted above
The present invention provides for a laminator and heated pressure roller arrangement that overcomes lateral shear stresses and overdrive conditions, and allows the use of low durometer rubber or of a compressible rubber.
The present invention further provides for a heated pressure roller that allows the use of a wider nip, and permits a wider range of media to be laminated.
The present invention further provides for a heated pressure roller that allows a wider range of conditions for lamination, and permits a wider range of media thicknesses to be laminated.
The present invention also provides for a heated pressure roller that overcomes or reduces image growth and overcomes or reduces image shift from one color to another. Additionally, the present invention provides for a heated pressure roller that overcomes or reduces defects such as creases, rivers or valleys.
According to a feature of the present invention, a laminating system for bonding, to a paper receiver stock, a thermal print media of the type including a carrier and a material to be applied to the paper receiver stock, includes an improved pair of heated pressure rollers through which a sandwich of thermal print media and paper receiving stock is fed. The pair of heated pressure rollers have been improved by adding, to at least one of the heated pressure rollers, a metal or plastic belt or tube over a rubber layer of the heated roller. This serves to prevent lateral stresses or overdrive conditions from acting on the thermal print media or paper receiving stock.
The present invention relates to a laminator assembly which comprises a first roller located on a first side of a media passage; and a second roller located on a second side of the media passage so as to oppose the first roller. A nip portion is defined between the first and second rollers so as to apply pressure to media in the media passage which passes through the nip portion. Each of the first and second rollers is a heated roller that comprises a heating core and a substantially solid layer which surrounds the heating core. At least one of the first and second rollers comprises a first deformable layer which surrounds the substantially solid layer and a second deformable layer which surrounds the first deformable layer and forms an outer surface of the xe2x80x9cat least onexe2x80x9d first and second rollers.
The present invention also relates to a laminating roller assembly for a laminator which comprises first and second opposing rollers; wherein one of the first and second opposing rollers comprises a heater core, a substantially solid or compressible layer which surrounds the heater core, a first deformable layer which surrounds the substantially solid or compressible layer and a second deformable layer which surrounds the first deformable layer and forms an outer surface of the one of the first and second opposing rollers.
The present invention also relates to a laminator assembly that comprises a first roller located on a first side of a media passage; and a second roller located on a second side of the media passage so as to oppose the first roller. A nip portion is defined between the first and second rollers so as to apply pressure to media in the media passage which passes through the nip portion; wherein at least one of the first and second rollers comprises a first deformable layer and a second deformable layer which surrounds the first deformable layer and forms an outer surface of the at least one of the first and second rollers to contain the rubber to prevent lateral sheer stresses and over drive conditions.
The present invention also relates to a laminator assembly that comprises a first roller located on a first side of a media passage; and a second roller located on a second side of the media passage so as to oppose the first roller. A nip portion is defined between the first and second rollers so as to apply pressure to media in the media passage which passes through the nip portion; wherein at least one of the first and second rollers comprises a first deformable layer and a second deformable layer which surrounds the first deformable layer and forms an outer surface of the at least one of the first and second rollers to contain the rubber to prevent the first deformable layer from destroying the bond and coming off the roller core.
The present invention further relates to a laminating method which comprises the steps of forming at least one deformable layer on at least one of first and second pressure rollers so as to increase a width of a nip portion between the first and second pressure rollers; and passing a media to be laminated between the first and second pressure rollers and through the nip portion having the increased width.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiments presented below.